This invention relates in general to certain new and useful improvements in an apparatus for making filament reinforced tubular members, and more particularly, to an improved apparatus of making centrifugally cast filament reinforced tubular members which are capable of withstanding both internal and external pressure loads, and which also include particulate matter as an integral part of the component structure.
In recent years, reinforced plastic composite materials have received widespread attention due to the advances available in fabricating such structures and due to the increased availability of raw materials. Furthermore, reinforced plastic pipe has achieved increasing prominence in many industries since the reinforced plastic composite exhibits many structural abilities which are not inherent in their metal counterparts.
Reinforced plastic pipes are commonly formed by generating a cylinder from a suitable filamentary material through continuously winding filaments on a removable mandrel. The filament strands are impregnated with curable resin material, either before application of the strands to the mandrel or upon application of the strands to the mandrel, followed by a curing of the structure and removal from the mandrel. Such a system is exemplified by U.S. Pat. No. 3,128,216. Another technique commonly used in the fabrication of reinforced plastic pipe is to generate a cylinder from a suitable filamentary material by continuously winding the filaments on a fixed mandrel, impregnating the filaments, curing the composite structure, and continually removing the formed structure from the mandrel. By appropriate selection of the filamentary material and the binder, strong corrosion resistant structures can be fabricated.
Due to the high strength of fiberglass filaments and similar types of filamentary materials, such structures are capable of withstanding substantial internal pressure loads. In many applications, particularly for large diameter pipe, such as in underground pipe lines, the wall thickness is dictated by the external pressures and nonuniform loading produced by the ground loading rather than the internal pressures. Thus, the pipe structure is required to have a wall thickness which is substantially heavier than would be necessary to withstand internal pressures normally encountered. Inasmuch as the cost of raw materials needed for reinforced plastic pipe capable of withstanding a given external pressure load is substantially greater than the cost of counterpart materials, such as reinforced concrete or steel, the latter materials are generally used in pipe manufacture where the pipe is to withstand heavy external pressure loading, even though reinforced plastic pipe has generally superior physical and chemical properties.
In order to obviate this problem, there have been certain attempts to incorporate small inert particulate matter such as sand, similar spherical particles, and the like in the reinforced plastic composite. In addition, it has been proposed to form large diameter reinforced plastic pipe in the form of laminated structures. Such a structure consists of a thin layer of glass filaments and a layer of resin matrix as a first layer surrounded by a thick mass of core material of inert matter capable of withstanding compressive loading. When the cylindrical structure is subject to external loads, however, the deformation of the cross section is resisted by sheer loads at the interfaces between the core material and the reinforced plastic and failure of the structure occurs at the bond between these materials.
It is, therefore, the primary object of the present invention to provide a method and apparatus for the production of filament reinforced tubular members capable of withstanding both internal and external pressure loadings.
It is another object of the present invention to provide a method and apparatus of the type stated for manufacturing filament reinforced tubular members by centrifugally casting the filamentary material and adding a resinparticulate matter composition to the filamentary material to thereby form a composite.
It is an additional object of the present invention to provide an apparatus for producing filament reinforced tubular members on a mass-production basis which eliminates the necessity of employing conventional filament winding techniques and manually directed spray-up.
It is also an object of the present invention to provide an apparatus and method of the type stated which is readily adaptable to produce tubular members of a wide variety of sizes and cross sectional shapes.
It is a further object of the present invention to provide filament reinforced tubular members which inherently includes all of the necessary physical capabilities and mechanical attributes normally found in conventional filament wound tubular structure, but which eliminates the undesirable conventional filament winding techniques.
With the above and other objects in view, our invention resides in the novel features of form, construction, arrangement, and combination of parts presently described and pointed out in the claims.